Terahertz Multiple Beam Steering Using Graphene Pancharatnam-Berry Metasurfaces

Abstract

Pancharatnam-Berry metasurfaces have the great advantage of manipulating electromagnetic wave. At the same time, graphene has attracted much attention due to its unique electromagnetic responses in different Fermi levels. Here, graphene-based Pancharatnam-Berry metasurfaces are numerically built to achieve beam steering in terahertz band. When graphene is in the low Fermi level 0.01 eV, eight meta-atoms are designed to form a gradient Pancharatnam-Berry phase. After Pancharatnam-Berry phase is formed, a dual-beam metasurface is constructed, and then a gradient metsurface is designed to produce anomalous reflection. Finally, convolution operation is used to design two metasurfaces, and they generate dual- and quad-beams under circular and linear polarizations, respectively. Therefore, the designed metasurfaces can generate multiple beams in space. When graphene is in the high Fermi level 0.50 eV, phase difference between eight meta-atoms disappears, and only mirror reflection exists. Meanwhile, there must be a middle value in Fermi level of graphene to get multiple beams. At this moment, there are anomalously reflected beams and mirror beam. Using different responses of graphene in different Fermi levels, beam steering is achieved in terahertz band. Our design may provide a method for beam steering and terahertz communication.